Sweat soldering has long been used for the supply and distribution of potable water, especially in single family residential constructions, due to its durability and the relative ease with which solder connections were made. Modern changes to various plumbing codes, which mandate lead-free solders and water soluble fluxes, have, however, greatly increased the difficulty in making sweat solder connections as these lead-free solders and water soluble fluxes tend to be less tolerant of certain variables (e.g., the presence of oxidation or the use of excessive heat) than the lead-based solders and acid-based fluxes that had been previously used.
Furthermore, the sweat soldering task is relatively time consuming as compared to the crimp-type connections that are employed in a PEX (i.e., cross-linked polyethylene) system. A PEX system utilizes lengths of plastic PEX tubing, barbed fittings (which are inserted into the PEX tubing) and collars that are employed to crimp the tubing to the fitting. As the crimping operation may be accomplished in roughly ¼ to ½ the time that is necessary to complete the soldering of a sweat solder joint, plumbing contractors have observed the potential for substantial savings in labor costs by utilizing a PEX system.
In an effort to eliminate the disadvantages of sweat solder connections, manufacturers such as Viega, have introduced fittings that may be crimped directly to conventional lengths or sticks of hard drawn copper tubing. The ProPress system marketed by Viega includes an inner O-ring seal that is carried on the inner diameter of the fitting; the O-ring sealingly engages the tubing upon insertion of the tube into the fitting. A crimping tool is subsequently employed to crimp the fitting to thereby fix the fitting and the tube to one another. This system, however, is known to suffer from several drawbacks.
One such drawback concerns the sealing of the fitting to the outside surface of the copper tubing. It is well known in the art that the outside surface of a copper tube is relatively susceptible to imperfections during its formation via extrusion, such as gouges or scratches, as well as relatively susceptible to damage during shipping and storage. As such imperfections and damage may adversely affect the ability of the fittings to seal against the outer surface of the tubing, manufacturers of the copper tubing typically subject the extruded sticks of tubing to an eddy current test to verify the integrity of each stick's outside surface. This testing is costly and as we have found, leaks are possible even when the tubing conforms to published standards. Accordingly, it appears that a relatively time consuming manual inspection must be made of each tube prior to its coupling to a fitting.
Another drawback concerns the incompatibility of the known systems with lengths of annealed copper tubing. In this regard, the annealed copper tubing is readily deformable so that the crimping process fails to secure the fitting and the annealed copper tubing together. Accordingly, plumbing contractors must equip themselves with two discrete sets of fittings: one set of crimp fittings that is compatible with the hard drawn sticks of tubing, and another set (e.g., flare or compression fittings) that are compatible with the annealed coils of tubing.
In view of the aforesaid drawbacks, there remains a need in the art for an improved fluid conduit system that permits the joining of all types of copper tubing with one style of fitting.